If you ask about solar energy directly converted to electrical energy, then GaurdianFox has nailed it: electrochemical batteries and an inverter. The batteries can be lead-acid, lithium ion, nickel-cadmium, or the old iron-caustic "Edison cells." Each has pros & cons. Cost, availability, danger, size and expected lifetime are all important factors.

If you want to add another step, consider using the electricity from your PV panels to pump water into an elevated tank; releasing the water through an in-line turbine will generate electricity after the sun has set.

There are lots of schemes to convert the sun's radiant energy to some kind of usable power: read up on the parabolic reflectors and steam engines used in the late 1800s off the coast of Chile to mine bird guano... much prized in Europe as fertilizer. Try to find a book called "The Golden Thread" for information about solar power going back 3,000 years.

There's really only one practical way to store solar energy. You store it in batteries. What type of battery is dependant on the project, but deep-cycle 12v car batteries are popular for solar homes and boats. A solar panel, AKA a photovoltaic panel, is what converts solar energy into electricity. If you mean to ask how to convert it into household AC 120v current, then the answer is you need to connect an inverter to the batteries which you've been storing your collected energy in.